dirwait is a simple command line utility for Windows that can wait until the contents of a directory (and optionally, its subdirectories) have been modified. It can be useful when used with batch files to automatically build or process source code after it has been saved in an editor, e.g. using a batch file like:

@echo off
<some processing command goes here>
goto loop

It is written in C and should compile under any Windows C compiler. Download the archive here (16K) which contains a windows executable (which you can put it in your system PATH) and the source code under zlib license.

For usage information run dirwait like dirwait --help:

Usage: dirwait [-d path] [-s] [-t milliseconds]
If -d is not given, dirwait will wait for changes in the current directory
If -s is given, subdirectories will also be monitored
If -t is given, a timeout of the given milliseconds is used

You may also want to check out sendkeys which can be used to send keys to specific windows (for e.g. sending F5 to your browser right after a processing command).